There are many tools that can monitor folder(s) on a Mac and upload them to your Flickr account or any cloud account when there is any newly added photo. The photo which gets uploaded automatically will be posted with privacy set to private. One such tool that does exactly this is PicBackMan. PicBackMan's Flickr Uploader for Mac is an automated tool that can effortlessly upload photos / videos form you Mac machine to your Flickr account.
Once when you associate a photo or video folder with the desktop application, it keeps a check on any new additions. As and when it finds new photos added to the associated folder, it auto uploads it to Flickr. The privacy setting is 'Private'. Later on you can login in to your Flickr account to make changes to the privacy settings.
PicBackMan Flickr uploader for Mac is the best solution if you are looking for an auto-uploader to upload photos to Flickr on Mac OSx